Technology is known for embedding information, known as watermark information, into image data. Embedding information into image data sometimes results in the embedded information becoming image noise, leading to image quality degradation, and technology that suppresses image quality degradation has therefore been proposed. Examples of such technology include a first technology in which frames with embedded watermark information and frames with embedded inverted information of the watermark information are provided in order to make the watermark information difficult to perceive by the human eye. There is also a second technology that suppresses image quality degradation by causing a number of regions where watermark information is embedded to periodically change as time elapses, and causing the average color of an image overall to periodically fluctuate as time elapses.